To complete one Novena, a person must say the Rosary for 9 days. Three Novenas of 9 days must be said to obtain the favour. Then, three more Novenas must be said in Thanksgiving. In total, there must be 27 days of Rosary prayers to obtain the favour and 27 days of Rosary prayers in Thanksgiving. This makes a total of 54 days.
Whether the prayer intention has been received or not after the first 27 days (3 Novenas), the person must still say the 3 Rosary prayer Novenas (27 days) in Thanksgiving.
From day to day, the meditations are in accordance with the guideline followed in the Catholic Church. These included the Joyful Mysteries, the Sorrowful Mysteries, the Glorious Mysteries and the Mysteries of Light.
WHERE THIS TRADITION CAME FROM:
Church history reveals to us that on March 3, 1884, Our Lady of Pompeii appeared before the gravely ill daughter of an Italian military officer. Through her, Our Lady gave the world the miraculous devotion of the 54 days Rosary Novena.
For over a year, Fortuna Agrelli had been in great distress even near death. So serious was her illness that her case had been given-up as hopeless by the most celebrated physicians. In desperation, on February 16 th, the afflicted girl and her family began a novena of Rosaries.
One evening two weeks later, the Queen of the Holy Rosary appeared to Fortuna. Sitting upon a high throne, surrounded by luminous figures, Our Lady was holding the Divine Child on her lap and a Rosary in her hand. Both were arrayed in golden garments and were accompanied by Sts. Dominic and Catherine of Siena.
Our Lady said, “Child, your faith has pleased me. Whoever desires to obtain favours from me should make three Novenas of the prayers of the Rosary, and three Novenas in thanksgiving.”
Obedient to Our Lady’s invitation, Fortuna and her family completed the six novenas whereupon the young girl was restored to perfect health and her family showered with many blessings.
With Special Thanks to http://www.catholicdoors.com/prayers/novenas/p00074.htm